Satellite communications providers face significant risk when the link to a satellite is disrupted. Critical applications go offline, customers lose confidence, and revenue is lost as providers scramble to recover the link. Thus, most satellite earth stations employ brute-force redundancy, i.e. two of everything, to reduce the risk, but at significant cost and increased complexity. When the final amplifier stage was a single tube and thus a single point failure, having a second amplifier immediately available was a pragmatic solution. However, with the demonstrated viability and practicality of solid-state amplifiers, non-brute-force redundancy solutions offer significant cost and performance advantages.

ModuMAX Power Options

C-Band SSPAs

1500 Watts

1000 Watts

800 Watts

X-Band SSPAs

1250 Watts

1000 Watts

700 Watts

Ku-Band SSPAs

800 Watts

500 Watts

350 Watts

Phase-Combined Systems

C-Band

3000 Watts

2000 Watts

X-Band

2500 Watts

2000 Watts

Ku-Band

1500 Watts

1000 Watts

Built-in Redundancy

Solid-state power amplifiers (SSPAs) consist of multiple transistors in parallel, and consequently contain built-in redundancy. Because of forward thinking design, including multiple parallel RF modules, power supplies and cooling fans, General Dynamics ModuMAX SSPAs are extremely reliable and fault-tolerant. With the ModuMAX series, one fault-tolerant SSPA can replace two conventionally designed high power amplifiers yielding significant installation savings and reduced operating costs.

Configurable Power

A ModuMAX SSPA combines the RF output power from eight identical, fully interchangeable RF plug-in modules (16 in a phase-combined system) to obtain the rated power capacity. These amplifier modules can be individually turned on or off via either local or remote control. Installations can exploit this feature of the ModuMAX SSPA to reduce prime power consumption during times when the required RF output power is lower than the maximum linear power capacity of the amplifier.

Additionally, the amplifier modules can also be employed in a redundancy configuration where, in the event of a fault occurring in the online modules, spare modules can be brought on line rapidly via M&C. Configurable power, the ability to adjust the number of enabled modules to match the system output power requirements or configure the modules in a redundant array, is a key feature of the ModuMAX design.

Configurable power is implemented by determining the minimum number of modules that must be enabled to provide the required RF output power. To use configurable power, determine how many RF modules must be on line to meet the required power while leaving the remaining modules offline. Any modules not needed to support the system traffic load are deactivated, either locally or via one of the remote interfaces. When the system is operating, the remote M&C system monitors the ModuMAX for faults. If the M&C system detects a fault in an enabled amplifier module, it immediately enables one of the deactivated modules to compensate for the loss. No minimum warmup time is required; the amplifier modules become functional immediately upon enabling.

Configurable power allows prime power consumption to be significantly reduced by deactivating modules while still meeting the system RF power requirements. While power consumption is approximately proportional to the number of enabled modules, RF output capacity decays as shown in Table 1.

ModuMAX SSPAs can also be phase-combined in a single rack utilizing a fixed (hybrid) or variable (VPC) phase combining system. The VPC system affords the operator the flexibility to configure the system for operation using either ModuMAX SSPA individually (single mode), or using both simultaneously (phase-combined mode) to nearly double the system output power. A ModuMAX system based on a VPC has a total of 16 RF modules (8 in each of 2 RF units), together with power supplies and the VPC sub-system contained in a single rack.

RF Plug-In Modules

The RF plug-in modules are conveniently accessible from the front panel. Summary module status is visually indicated by a multicolor indicator on each module with detailed information available at the control panel display.

Failure of a single module causes a drop of approximately 1.2 dB in output power—without the momentary loss of signal caused by redundant switchover systems (Table 1). Defective RF modules can be hot-swapped while the SSPA continues to operate. Since they contain only a fraction of the RF power transistors in the SSPA, spare RF modules are affordable.

Easy to Operate and Maintain

ModuMAX SSPAs are designed to be easy to operate and maintain. All features can be fully remote controlled through standard RS-232/-422/-485 and network interfaces. For quick and easy manual access, the most commonly used controls are located on the front panel.

Most maintenance can be performed safely while the SSPA continues to operate. Any of the eight fans in the aircooling system can be easily removed and replaced, without ever taking the SSPA off-line. Even the power supply modules are redundant and hot swappable.

Phase-Combined Systems

A ModuMAX system is easily expandable. Phase-combine two SSPAs for double the power output using only 61.25" (35 RU) of rack space (High power systems with two PS chassis per RF unit require 71.75" [41 RU]). With 16 phase combined RF modules, one failed module causes only about 0.6 dB drop in output power.

Global EMC and Safety Compatibility

Cooling System

ModuMAX also incorporates redundancy into its integral forced-air cooling system. Sufficient cooling margin is built into the design to tolerate the loss of one cooling fan. Fans are monitored for rotational speed, and failure of a fan is indicated on the control panel display. In the event of a fan failure, the SSPA can continue to operate until a replacement is installed. The air cooling system utilizes separate rear panel air intake and exhaust ducts and can be vented either outdoors or into the room.

Power

For most systems, operating power is supplied by three identical plug-in power supply modules in a rack-mount chassis; higher output systems require six modules (two PS chassis) per RF unit for full redundancy. If a module fails, the remaining ones can supply 100% of the required load current and the defective module can be hot-swapped without interruption.